CN111896391B - Method for measuring elastic modulus of solder in reflow soldering process based on difference method - Google Patents
Method for measuring elastic modulus of solder in reflow soldering process based on difference method Download PDFInfo
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- CN111896391B CN111896391B CN202010793383.8A CN202010793383A CN111896391B CN 111896391 B CN111896391 B CN 111896391B CN 202010793383 A CN202010793383 A CN 202010793383A CN 111896391 B CN111896391 B CN 111896391B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/18—Performing tests at high or low temperatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
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- G01N2203/0226—High temperature; Heating means
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Abstract
The invention discloses a method for measuring the elastic modulus of solder in a reflow soldering process based on a difference method, which is used for solving the problem that the contact part of copper foil and the solder can not react to generate an interface metal layer in the reflow soldering process when the elastic modulus of the solder is measured in the prior art. The method comprises the following implementation steps: 1. setting a measuring device; 2. measuring the stress value and the strain value of the copper foil in each temperature area; 3. measuring the stress value and the strain value of the copper foil of each temperature area reacting with the solder; 4. respectively calculating the elastic modulus of the copper foil of each temperature area and the elastic modulus of the copper foil of each temperature area reacting with the solder by using an elastic modulus formula; 5. calculating the elastic modulus of the solder in each temperature zone by using a difference method; 6. and fitting the elastic modulus of the solder in each temperature zone into a curve. The invention has the advantage of more accurate measurement of the elastic modulus of the solder in the reflow soldering process.
Description
Technical Field
The invention belongs to the technical field of electronics, and further relates to a difference method-based method for measuring the elastic modulus of solder in a reflow soldering process in the technical field of experimental measurement. The method can be used for measuring the stress value and the strain value of the copper foil and the reaction of the copper foil and the solder in the reflow soldering process, and the elastic modulus of the copper foil and the reaction of the copper foil and the solder is calculated by using an elastic modulus formula.
Background
With the continuous emergence of various novel electronic products and the continuous improvement of the living standard of people, people also put forward new demands on the quality of the electronic products, and the electronic products are continuously developing towards miniaturization, lightness and thinness and high density. Accordingly, a significant challenge is posed to the surface mounting technology, which is a kind of surface mounting technology. The reflow soldering technology is that a mainboard is placed in a reflow oven with a heating circuit inside, air or nitrogen is heated to a high enough temperature and then blown to a circuit board with a mounted element, and solder on two sides of the element is melted and then bonded with the mainboard. The reflow curve is set according to various parameters of the solder in the reflow soldering process, and the setting of the reflow curve can directly influence the bonding quality of the element and the mainboard, so that the accuracy of measuring the elastic modulus of the solder is necessary to be improved. The measurement of the modulus of elasticity of solder is a technique in the field of electronic technology, and there are currently established techniques for measuring the modulus of elasticity of solder alone. However, in the reflow soldering process, the contact part of the solder and the copper foil can react to generate an interface metal layer, and the influence of the above situation on the elastic modulus of the solder is difficult to consider in the prior art, so that the measurement of the elastic modulus of the solder in the reflow soldering process still has a lot of defects.
A method for measuring the elastic modulus of solder at different temperatures is provided In a paper 'Sn-Zn-Bi-In-P novel lead-free solder mechanical parameter measurement and analysis' published by Hongjiao, zhang Bo and Mazuheng. The method uses a WDW-20 microcomputer control variable temperature creep testing machine to respectively carry out tensile measurement at the temperature of 25 ℃, 50 ℃, 75 ℃, 100 ℃ and 125 ℃, and the strain gauges are attached to the front side and the back side of a solder sample to collect axial strain data and transverse strain data, and the elastic modulus of the solder sample can be obtained according to the loading load and the axial strain data and the transverse strain data. Although the method can well measure the elastic modulus of the single solder, the method still has the defect that the problem that the contact part of the copper foil and the solder reacts to generate an interface metal layer in the reflow soldering process cannot be considered when the elastic modulus of the solder is measured, so that the measurement of the elastic modulus of the solder is inaccurate.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for measuring the elastic modulus of solder in the reflow soldering process based on a difference method, so as to solve the problem that the contact part of copper foil and the solder in the reflow soldering process can not react to generate an interface metal layer in the measurement of the elastic modulus of the solder.
The specific idea for realizing the purpose of the invention is as follows: firstly, respectively measuring the stress value and the strain value of each temperature zone copper foil and the stress value and the strain value of each temperature zone copper foil reacting with the solder, then respectively calculating the elastic modulus of each temperature zone copper foil and the elastic modulus of each temperature zone copper foil reacting with the solder by using an elastic modulus formula, then calculating the elastic modulus of each temperature zone solder by using a difference method, and finally fitting the elastic modulus of each temperature zone solder into a curve to obtain an elastic modulus curve of the solder changing along with the temperature zones.
The method for realizing the aim of the invention comprises the following steps:
(1) Setting a measuring device:
(1a) Fixing a bolt reversely passing through a threaded through hole in the center of the groove on the copper foil by using a nut, and fixing the copper foil with the groove in the center on the support by using the bolt and the nut to obtain an operating mechanism in the measuring device, wherein the copper foil and the support are equal in length, and strain gauges are uniformly adhered to the lower surface of the copper foil;
(1b) Zeroing the strain gauge and the pressure sensor, checking the sensitivity of the strain gauge and the pressure sensor, and connecting the strain gauge on the lower surface of the copper foil with the pressure sensor and the strain gauge through a lead to obtain a signal acquisition unit in the measuring device;
(2) Measuring the stress value and the strain value of the copper foil in each temperature area:
(2a) Rotating a nut on a bolt positioned in the center of a copper foil groove to apply a force load to the surface of the copper foil, and placing an operating mechanism on a conveyor belt of a reflow oven until the copper foil is obviously deformed;
(2b) When the conveyor belt passes through each temperature zone of the reflow oven, recording stress values and strain values of the copper foil, which are acquired by a pressure sensor and a strain gauge in a signal acquisition unit through a strain gauge;
(3) Measuring the stress value and the strain value of the copper foil in each temperature area reacting with the solder:
(3a) After the stress value and the strain value of the copper foil in all temperature areas are acquired by a pressure sensor and a strain gauge in a signal acquisition unit, taking out an operating mechanism from a reflow furnace, rotating a nut on a bolt positioned in the center of a copper foil groove, taking down the nut from the bolt, and then placing solder in the groove of the copper foil;
(3b) Placing the nut on the bolt positioned in the center of the copper foil groove, then rotating the nut again to apply force load to the surface of the solder, and placing the operating mechanism on a conveying belt of a reflow oven until the solder and the copper foil are obviously deformed;
(3c) When the conveyor belt passes through each temperature zone of the reflow oven, recording stress values and strain values of the reaction between the copper foil and the solder, which are acquired by a pressure sensor and a strain gauge in a signal acquisition unit through a strain gauge;
(3d) After the stress value and the strain value of the reaction between the copper foil and the solder in all temperature areas are acquired by the pressure sensor and the strain gauge in the signal acquisition unit, taking the operating mechanism out of the reflow furnace;
(4) Respectively calculating the elastic modulus of the copper foil of each temperature area and the elastic modulus of the copper foil of each temperature area reacting with the solder by using an elastic modulus formula;
(5) And (3) calculating the elastic modulus of the solder in each temperature zone by using a difference method:
using the difference formula C n ＝A n -B n Calculating the elastic modulus of the solder in each temperature zone, wherein C n The modulus of elasticity, A, of the solder in the nth temperature zone is shown n Elastic modulus of reaction between copper foil of nth temperature zone and solder, B n The elastic modulus of the copper foil in the nth temperature zone is shown;
(6) The modulus of elasticity of the solder in each temperature zone is fitted to a curve.
Compared with the prior art, the invention has the following advantages:
the invention utilizes a difference method to calculate the elastic modulus of the solder in each temperature zone in the reflow soldering process, and takes the copper foil and the solder as a whole to calculate the elastic modulus of the reaction between the copper foil in each temperature zone and the solder in the reflow soldering process, thereby overcoming the problem that the contact part of the copper foil and the solder in the reflow soldering process can react to generate an interface metal layer when the elastic modulus of the solder in the reflow soldering process is measured in the prior art, and ensuring that the measurement of the elastic modulus of the solder in the reflow soldering process is more accurate.
Drawings
FIG. 1 is a schematic view of the operating mechanism of the apparatus of the present invention;
FIG. 2 is a flow chart of the method of the present invention.
Detailed Description
The invention is further described below with reference to fig. 1 and 2.
Step 1, setting a measuring device.
Referring to fig. 1, the operating mechanism of the device of the invention is schematically shown and comprises a bolt nut 1, a copper foil 2, a bracket 3 and a bolt nut 4.
And reversely passing the bolt of the bolt and nut 1 through the threaded through hole in the center of the groove of the copper foil 2, fixing the bolt of the bolt and nut 1 on the copper foil 2 by using the nut of the bolt and nut 1, sequentially and vertically penetrating four bolts of the bolt and nut 4 through the threaded through holes in the four corners of the copper foil 2 and the bracket 3 respectively, fixing the middle of the copper foil 2 and the bracket 3 and the lower surface of the bracket 3 by using the nut of the bolt and nut 4, and obtaining an operating mechanism in the measuring device, wherein the interval between the copper foil 2 and the bracket 3 is 1 cm.
Bolt and nut 1 in proper order perpendicularly runs through the lower and upper surface that lie in the screw thread through-hole at recess center to fix by the nut of recess upper surface, rotate the nut and can exert the force to the copper foil, the nut is used for fixing bolt and exerts the load.
The length of the copper foil 2 is 20cm, the width of the copper foil is 15cm, the thickness of the copper foil is 1cm, a groove with the length of 15cm, the width of 10cm and the thickness of 0.5cm is arranged in the center of the copper foil, threaded through holes with the diameter of 2cm are respectively arranged at the four corners of the copper foil and the center of the groove, the groove is used for placing soldering paste, and strain gauges are uniformly adhered to the lower surface of the copper foil.
The length of the support 3 is 20cm, the width of the support is 15cm, the thickness of the support is 1cm, and four corners of the support are respectively provided with a threaded through hole with the diameter of 2 cm.
The bolt and nut 4 is composed of four bolts and eight nuts, the four bolts respectively vertically penetrate through the upper surface and the lower surface of the threaded through holes in the copper foil and the four corners of the support in sequence, and the bolts are fixed by the nuts in the middle of the copper foil and the support and the lower surface of the support.
And zeroing the strain gauge and the pressure sensor, checking the sensitivity of the strain gauge and the pressure sensor, and connecting the strain gauge on the lower surface of the copper foil with the pressure sensor and the strain gauge through a lead to obtain a signal acquisition unit in the measuring device.
The strain gauge is used for measuring the stress and strain of the copper foil in each temperature area and the reaction between the copper foil and the solder.
The pressure sensor is used for collecting stress values of the copper foil of each temperature area and the reaction of the copper foil and the solder.
The strain gauge is used for acquiring the strain value of the copper foil of each temperature area and the reaction between the copper foil and the solder.
And 2, measuring the stress value and the strain value of the copper foil of each temperature area.
And rotating a nut on the bolt positioned in the center of the copper foil groove to apply a force load to the surface of the copper foil, and placing the operating mechanism on a conveying belt of a reflow oven after the copper foil is obviously deformed.
When the conveyor belt passes through each temperature zone of the reflow oven, the stress value and the strain value of the copper foil, which are acquired by the pressure sensor and the strain gauge in the signal acquisition unit through the strain gauge, are recorded.
And 3, measuring the stress value and the strain value of the reaction of the copper foil of each temperature area and the solder.
And after the stress value and the strain value of the copper foil in all temperature areas are acquired by the pressure sensor and the strain gauge in the signal acquisition unit, taking out the operating mechanism from the reflow furnace, rotating the nut on the bolt positioned at the center of the copper foil groove, taking off the nut from the bolt, and then placing the solder in the groove of the copper foil.
And placing the nut on the bolt positioned in the center of the copper foil groove, then rotating the nut again to apply force load to the surface of the solder, and placing the operating mechanism on a conveying belt of a reflow oven until the solder and the copper foil are obviously deformed.
When the conveyor belt passes through each temperature zone of the reflow oven, the stress value and the strain value of the reaction between the copper foil and the solder, which are acquired by the pressure sensor and the strain gauge in the signal acquisition unit through the strain gauge, are recorded.
And when the stress value and the strain value of the reaction between the copper foil and the solder in all temperature areas are acquired by the pressure sensor and the strain gauge in the signal acquisition unit, taking the operating mechanism out of the reflow furnace.
And 4, respectively calculating the elastic modulus of the copper foil of each temperature area and the elastic modulus of the copper foil of each temperature area reacting with the solder by using the following elastic modulus formula:
wherein, E n Expressing the elastic modulus, σ, of the copper foil in the nth temperature zone or the reaction between the copper foil and the solder n The stress value epsilon of the reaction between the copper foil of the nth temperature zone or the copper foil and the solder collected by the pressure sensor is shown n And the strain value which is acquired by the strain gauge and reacts with the copper foil in the nth temperature zone or the copper foil and the solder is represented.
And 5, calculating the elastic modulus of the solder in each temperature area by using a difference method.
Using the difference formula C n ＝A n -B n Calculating the elastic modulus of the solder in each temperature zone, wherein C n Denotes the modulus of elasticity, A, of the solder in the nth temperature zone n The modulus of elasticity of the copper foil in the nth temperature zone in reaction with the solder is shown, B n The elastic modulus of the copper foil of the nth temperature zone is shown.
And 6, fitting the elastic modulus of the solder in each temperature zone into a curve.
Claims (2)
1. A method for measuring the elastic modulus of a solder in a reflow soldering process based on a difference method is characterized in that a pressure sensor and a strain gauge are respectively used for collecting the stress value and the strain value of the copper foil of each temperature zone and the reaction of the copper foil and the solder, and the elastic modulus of the solder of each temperature zone is calculated by using the difference method, wherein the method comprises the following steps:
(1) Setting a measuring device:
(1a) Fixing a bolt reversely passing through a threaded through hole in the center of the groove on the copper foil by using a nut, and fixing the copper foil with the groove in the center on the support by using the bolt and the nut to obtain an operating mechanism in the measuring device, wherein the copper foil and the support are equal in length, and strain gauges are uniformly adhered to the lower surface of the copper foil;
(1b) Zeroing the strain gauge and the pressure sensor, checking the sensitivity of the strain gauge and the pressure sensor, and connecting the strain gauge on the lower surface of the copper foil with the pressure sensor and the strain gauge through a lead to obtain a signal acquisition unit in the measuring device;
(2) Measuring the stress value and the strain value of the copper foil in each temperature area:
(2a) Rotating a nut on a bolt positioned in the center of the copper foil groove to apply a force load to the surface of the copper foil, and placing an operating mechanism on a conveying belt of a reflow oven until the copper foil is obviously deformed;
(2b) When the conveyor belt passes through each temperature zone of the reflow oven, recording stress values and strain values of the copper foil, which are acquired by a pressure sensor and a strain gauge in a signal acquisition unit through a strain gauge;
(3) Measuring the stress value and the strain value of the reaction of the copper foil of each temperature area and the solder:
(3a) After the stress value and the strain value of the copper foil in all temperature areas are acquired by a pressure sensor and a strain gauge in a signal acquisition unit, taking out an operating mechanism from a reflow furnace, rotating a nut on a bolt positioned in the center of a copper foil groove, taking down the nut from the bolt, and then placing solder in the groove of the copper foil;
(3b) Placing the nut on the bolt positioned in the center of the copper foil groove, then rotating the nut again, applying force load to the surface of the solder, and placing the operating mechanism on a conveying belt of a reflow oven after the solder and the copper foil are obviously deformed;
(3c) When the conveyor belt passes through each temperature zone of the reflow oven, recording stress values and strain values of the reaction between the copper foil and the solder, which are acquired by a pressure sensor and a strain gauge in a signal acquisition unit through a strain gauge;
(3d) After stress values and strain values of the copper foil reacting with the solder in all temperature areas are acquired by a pressure sensor and a strain gauge in a signal acquisition unit, taking the operating mechanism out of the reflow furnace;
(4) Respectively calculating the elastic modulus of the copper foil of each temperature area and the elastic modulus of the copper foil of each temperature area reacting with the solder by using an elastic modulus formula;
(5) And (3) calculating the elastic modulus of the solder in each temperature zone by using a difference method:
using the difference formula C n ＝A n -B n Calculating the elastic modulus of the solder in each temperature zone, wherein C n Denotes the modulus of elasticity, A, of the solder in the nth temperature zone n The modulus of elasticity of the copper foil in the nth temperature zone in reaction with the solder is shown, B n Expressing the elastic modulus of the copper foil in the nth temperature zone;
(6) The modulus of elasticity of the solder in each temperature zone is fitted to a curve.
2. The method for measuring the elastic modulus of the solder in the reflow soldering process based on the difference method as claimed in claim 1, wherein the elastic modulus in the step (4) is as follows:
wherein, E n Expressing the elastic modulus, σ, of the copper foil in the nth temperature zone or the reaction between the copper foil and the solder n The stress value epsilon of the copper foil of the nth temperature zone or the reaction of the copper foil and the solder, which is collected by the pressure sensor n And the strain value of the copper foil of the nth temperature zone or the reaction between the copper foil and the solder, which is acquired by the strain gauge, is represented.
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| CN111408549A (en) * | 2020-03-24 | 2020-07-14 | 广东长盈精密技术有限公司 | Device and method for testing welding effect of copper foil |
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2020
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| SU1400825A1 (en) * | 1986-06-12 | 1988-06-07 | Предприятие П/Я Р-6476 | Method of cold pressure welding of aluminium and copper foil |
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